The invention relates to the maintenance of floors and specifically to a method of maintaining floor surfaces using a single cleaning solution. The solution is used first at full strength followed by multiple cleanings with a dilution of the same solution to maintain an effective coefficient of friction, thereby reducing the probability of slipping and falling.
Hard floor surfaces in commercial and institutional establishments including restaurants, commercial kitchens, hospitals, laboratories and retail stores often become relatively slippery after use and repeated cleanings, leading to slip and fall injuries. Both employees and customers can be injured in slips and falls resulting in significant expense for medical attention, Workers"" Compensation costs, lost time and liability-associated costs, such as insurance premiums, compensatory awards and/or settlement costs. In the food industry, slip and fall injuries to employees can also include indirect injuries such as when the employee touches a hot surface while attempting to arrest a fall and is burned.
Hard floor surfaces, when clean and new, have an inherent coefficient of friction (COF) characteristic of the surface material. The COF is generally defined as the amount of force parallel to a surface that is required to move or make slip a force or weight that is normal to the surface, divided by the weight. Rougher surfaces generally have a higher COF whereas smoother surfaces have a lower COF.
COF can be measured using the American Society for Testing and Materials (ASTM) Test C 1028-89. This test is the U.S. ceramic tile industry""s standard test for assessing the slip resistance of ceramic tile and other like surfaces. The test is used to measure the frictional force between a flooring surface and a slider made of laboratory grade Neolite, a synthetic rubber. The test result can be expressed as a static COF. The term static is used because the two surfaces are at rest with respect to each other when the test is made.
The slider used in ASTM C 1028-89 is three inches square. The slider is first calibrated using a standard reference tile. The slider is then placed on the sample flooring surface and a 50 pound weight is placed on the slider. A dynamometer which measures force in pounds is used to pull the weighted slider to initiate a small movement across the flooring. This pulling force is then divided by the weight on the slider and the result, after correction using the slider calibration data, is equal to the static coefficient of friction.
The flooring can be tested both dry and wet with water. In each case, the COF is measured twelve times and the results are averaged. The ASTM test method specifies that each flooring sample should consist of three pieces of the tile. For each of the three pieces, a pull is made in each of four directions, e.g. north-east-south-west.
According to the Ceramic Tile Institute, a COF of greater than 0.6 is considered safe; a COF of between 0.5 to 0.6 is conditionally acceptable; and a COF less than 0.5 is considered unsafe.
The COF can be increased by the presence of macroscopic and microscopic variations in the surface. Macroscopically, a floor may include a pattern visible to the naked eye such as on tiles or in a terrazzo floor surface. Microscopically (e.g., when viewed at about a 450xc3x97 magnification), a new clean floor material typically has a non-smooth surface made up of peaks and valleys and a pore structure which present a shoe-gripping surface. Some hard surfaces, such as those on polished marble and granite, terrazzo and smooth ceramic tiles have a relatively low COF and therefore are generally more slippery. Other surfaces typically used in commercial flooring including grouted quarry tile or cemetitious concrete have a rougher surface texture resulting in a higher COF and a less slippery surface.
The COF of a hard surface can be altered over time by accumulation of fats and oils (collectively known as grease), accumulation of spilled food materials or other dirt, accumulation of cleaning residues especially from alkaline cleaning solutions, deposition of minerals from the water supply (water hardness), grout joint saponification or any combination of these factors. These accumulations generally fill the peaks and valleys and the pore structure of the surface making it smoother and lowering the COF. In commercial kitchens and restaurants, polymerization of fats and oils producing a hard, dense, greasy film is particularly responsible for increased slipperiness. Polymerized grease can reduce the COF of a floor surface about 50% in less than 30 days leading to an increased probability of slipping and falling by employees and patrons. Also, abrasion resulting from normal pedestrian traffic can lower the COF by polishing the surface over time. Abrasion polishing occurs especially on unglazed quarry tile surfaces.
Research in pedestrian safety has shown that the surface total mean peak-to-valley roughness (Rtm) is a good indicator of traction on surfaces wetted by water. The instrument used in this research is the Taylor Hobson Surtronic 10. The instrument has a stylus of radius of approximately 7 xcexcm. The stylus traverses a path of 0.8 mm and measures the height difference between the lowest valley and the highest peak. Five such paths are evaluated and the results electronically averaged for each reading on the instrument. Roughness can then be expressed as the average maximum peak-to-valley height difference in xcexcm. For reference, the approximate Rtm of some common materials is shown below in Table 1.
Cleaning of hard surface floors to remove accumulated deposits and restore the COF to that of the clean new surface can be accomplished in a number ways. Scrubbing or mopping with a cleaning solution that contains an alkaline emulsifier can temporarily restore a floor surface but often leaves a residue of soap scum which can itself build up and eventually fill the peaks and valleys and a pore structure of the surface. Alkaline cleaning solutions can also precipitate silicon and calcium in the water supply resulting in accumulation of mineral deposits, thus reducing the COF despite the removal of grease film. Scrubbing with a deck brush and hot water (67xc2x0 C./160xc2x0 F.) followed by vacuuming of the wet surface (xe2x80x9cwet vacxe2x80x9d) or squeegee removal of the solution containing the suspended dirt particles before thorough rinsing is effective at cleaning off grease film but requires expensive equipment and significant training of personnel in the use of the equipment.
Some of the types of the currently available cleaners include slip resistance packet cleaners (e.g., SAFETY-TRAC(copyright) by Kay Chemicals); powder alkaline cleaners (e.g., TIDE(copyright) by Colgate Palmolive); degreasers (e.g., RECOVER(copyright) by Dubois); sodium hypochlorite solutions (e.g., CLOROX(copyright)); alkaline-based steam cleaners (e.g., STEAM CLEANERS(copyright) by Union Carbide); and acid-based cleaners (e.g., DRACKET SURE-TRAC(copyright) by Bristol Meyers, SAFETY STEP(copyright) by Dynamic Research, and the cleaner disclosed in U.S. Pat. No. 5,223,168 issued to Holt). A number of additional liquid alkaline cleaners are available, such as REGAIN and MAXICLEAN by Ecolabs, POWERFOAM by SSDC Corporation and TITAN by Kay Chemical. However, all of the foregoing products suffer from a variety of drawbacks. Many of these products contain hazardous concentrations of chemicals, and therefore, require special care in use. Additionally, some of these products require multiple steps during their use (e.g., separate cleaning, restoring and neutralizing steps) or specialized equipment (e.g., steamer equipment). Moreover, most of these products are limited to a single use, and multiple products are required in order to adequately maintain a floor.
In addition to cleaning of the floor surface of accumulated grease, soil, mineral deposits and soap scum, restoration of the surface pore structure and peaks and valleys is important in improving floor texture, especially in areas of pedestrian traffic. Areas of pedestrian traffic include those in which employees and/or customers regularly walk during normal hours of operation of the commercial establishment. Restoration of surface irregularities has been accomplished by acid or mechanical etching (e.g., grit blasting) of floor surfaces. However, both processes have been found unsatisfactory because of exposure of personnel to highly acidic compounds, invasiveness of the cleaning procedure to normal commercial operations, and costs, particularly if a specialty contractor performs the procedure. Also, such etching procedures eventually weaken the floor tile surface. In addition, highly acidic solutions are subject to significant governmental regulation relating to health and safety during their use and transportation (i.e., those under OSHA and the Department of Transportation).
Surfaces that contain silicone dioxide components such as quarry tile have been treated with acidic solutions to etch the surface and thus restore a roughness to the floor. Treatments containing ammonium fluoride and hydrofluoric acid have long been known as agents for etching silicon substrates such as in the etching and frosting of glass or the treatment of silicone xe2x80x9cchipsxe2x80x9d for computer components as disclosed by Scardera et al. in U.S. Pat. No. 4,761,245 and Ohmi et al. in U.S. Pat. No. 4,795,582.
Commercially available hydrofluoric acid treatment solutions have a pH in the range from about 0.1 to about 2.4. Treatment of quarry tile with these highly acidic solutions requires multiple steps. After the surface is treated with the acidic solution, it must be neutralized (usually with extensive rinsing) and dried. The highly acidic treatment increases the COF but also results in deep pitting and undercutting to produce sharp platelets in the tile surface. The deep pits can collect fats, oils, and dirt, thus decreasing the COF over time. The sharp undercut platelets can cut mop strings thus damaging cleaning equipment and leading to accumulation of lint. The platelets rapidly wear down in areas of pedestrian traffic and thus result in repolishing of those surfaces where maintaining a relatively high COF is most important.
The Americans with Disabilities Act (ADA) requires that areas accessible to disabled persons be slip-resistant. The U.S. Department of Justice""s Access Board, which administers parts of ADA, in its Bulletin No. 4 recommends a minimum average static COF of 0.60 for level floors and 0.80 for ramps. This standard is also recommended by various other governmental and nongovernmental authorities, including the Ceramic Tile Institute and the City of Los Angeles. Not only must the initial flooring material meet these requirements, but the requirements for COF must also be met on an ongoing basis.
Hence, there is a need for a method of restoring floor surfaces in commercial and/or institutional establishments that both cleans and restores the uneven surface of the floor in a manner that can be performed easily and safely by employees of the establishment with a minimum of training and equipment. There is a need for a method that restores a floor""s COF without causing deep pitting or undercut platelet formation. Furthermore, there is a need for a method that employs chemical solutions that can be easily transported and safely used with standard levels of care (e.g., protective gloves and eye protection) without exposing personnel to highly acidic or alkaline solutions or toxic fumes.
One aspect of the present invention is a method for treating and maintaining a floor in a commercial or institutional establishment. The method has two components. In component (a), the following steps are performed at least once every five to ninety days: (i) applying an aqueous solution to the floor so as to restore the surface of the floor, the solution comprising a surfactant and a treating agent, the treating agent being either a fluoride-containing compound or an organic acid, the treating agent being in a concentration in the range 0.5 to 20% by weight, and the surfactant being in a concentration in the range 0.1% to 10.0% by weight, (ii) spreading the solution over the floor, and (iii) removing the solution from the floor. In component (b) the following steps are performed at least once every day that the commercial establishment is open and the steps of (a) are not performed: (i) applying the solution to the floor in a form which has been diluted from about 1 to 3 to about 1 to 500 in water, and (ii) cleaning the floor with the diluted solution. If desired, component (a) can be performed only on portions of the floor in the establishment that receive pedestrian traffic daily during normal operation of the commercial establishment. The spreading, removing and cleaning steps can be performed using a combination of abrasive scrubbing and mopping. In one such embodiment, the abrasive scrubbing and mopping is performed with a single device, such as a mop with an abrasive pad for abrasive point load mopping. The abrasive scrubbing can also be performed using a broom or deck brush.
In certain preferred embodiments, the treating agent is a fluoride-containing compound, such as hydrofluoric acid in a concentration in the range 0. 5 to 8% by weight or ammonium bifluoride in a concentration in the range 0. 5 to 20% by weight. Thus, in one embodiment, the treating agent is hydrofluoric acid in a concentration in the range of about 0.5% to about 8% by weight, more preferably in a concentration in the range of about 2.6% to about 8% by weight. In another embodiment, the treating agent is ammonium bifluoride in a concentration in the range of about 2 to about 4% by weight, more preferably in a concentration of about 2.5% by weight. In other embodiments, the treating agent is an organic acid, such as acetic acid, ascorbic acid, propionic acid, citric acid, glycolic acid, lactic acid, malic acid, tartaric acid, maleic acid, oxalic acid, malonic acid, sulfamic acid, fumaric acid, benzoic acid and gluconic acid.
The solution used can include a buffering agent. The pH of the solution is preferably in the range of from about 2.5 to 6.5, more preferably in the range of 3 to 6, and still more preferably in a pH range of 4.5 to 5.5. The solution used in component (b) has preferably been diluted from about 1 to 50 to about 1 to 300 in water, more preferably from about 1 to 100 to about 1 to 150 in water, and most preferably about 1 to 128 in water.
The surfactant can be a nonionic, anionic, amphoteric, ampholytic, zwitterionic or cationic detergent or a mixture thereof. In a preferred embodiment, the surfactant is nonylphenoxypolyethyloxyethanol in a concentration in the range 1.2 to 1.8% by weight.
The present invention relates to a method for maintaining floor surfaces in commercial and institutional establishments. Included within the commercial and institutional establishments to which the method of the present invention is applicable would be all non-residential developments as well as the common areas of multi-family residential developments.
In the method of the present invention, a single treating solution is used at different concentrations to maintain the floor surface at acceptable COF levels. The method comprises both a restoring phase and a cleaning phase. In the restoring phase, the floor is restored using a treating solution containing a surfactant and a treating agent to clean and restore the floor to its optimum COF. This step is repeated every five to ninety days that the establishment is in operation depending on the accumulation of grease and dirt. In order to save solution and time, the treating solution can be applied as a restorer only to those areas of heavy pedestrian traffic or areas in which greasy polymerization is a problem (e.g., areas of the kitchen near cooking machinery).
Abrasive point load mopping with a mop that combines an abrasive pad with strands of absorbent material is a mechanical means of breaking up and removing surface contaminants from a floor or other surfaces including cement walkways. A mop effective for abrasive point load mopping is disclosed in copending U.S. application Ser. No. 08/334,203, filed Nov. 4, 1994. Abrasive point load mopping can be used in conjunction with the method of the present invention in order to produce superior results.
The cleaning phase is generally conducted at least once a day. In the cleaning phase, the floor is maintained by cleaning with a dilution of between 1:3 and 1:500, more preferably 1:4 to 1:128, of the same solution in water. Under certain conditions, this cleaning step need not be performed on days when the restoring step is performed or when the establishment is not in operation.
In both the restoring and cleaning phases of the method, the treating solution can be applied to the floor with conventional mopping action, i.e. rotational movement using strands of absorbent material. The treating solution with the suspended grease and dirt can then be removed.
In one preferred embodiment of the method of the present invention, mopping in the cleaning and/or restoring phase is performed using a mop with an abrasive pad for abrasive point load mopping. Such a mop is described in co-pending U.S. patent application Ser. No. 08/334,203, filed Nov. 4, 1994, the disclosure of which is hereby incorporated by reference.
The treating solution used in the method of the present invention comprises an aqueous solution containing a surfactant and a treating agent. The treating agent can be any of a variety of fluoride-containing compounds in a concentration range from 0.5 to 20% by weight, more preferably 1 to 10%, and still more preferably 2 to 8% by weight. The percentages given are the full strength values used in the restoring phase of the method. Preferred fluoride-containing chemicals for use as treating agents include ammonium bifluoride (NH4HF2) and hydrofluoric acid (HF). When HF is used, it is most preferably in a concentration in the range 0.5 to 8% by weight. We have found that higher concentrations of HF are unduly corrosive when used in connection with the methods of the present invention.
In other embodiments of the invention, the treating agent can be an organic acid, which is also preferably in a concentration in the range of 0.5 to 20% by weight more preferably 1 to 10%, and more preferably 2 to 8%. Organic acids useful in this invention include monocarboxylic acid, saturated and unsaturated dicarboxylic acids, and hydroxycarboxylic acids. These include acids from the nonlimiting group of acetic acid, ascorbic acid, propionic acid, citric acid, glycolic acid, lactic acid, malic acid, tartaric acid, maleic acid, oxalic acid, malonic acid, sulfamic acid, fumaric acid, benzoic acid and gluconic acid.
As discussed above, many prior art floor restoration products include phosphoric acid (H3PO4). We have found that phosphoric acid is overly corrosive, and thus, preferably, phosphoric acid is either not present or present in a concentration less than 1%, still more preferably less than 0.5%, in the solutions used in connection with the method of the present invention.
The surfactant can be a nonionic, anionic, cationic, amphoteric, ampholytic or zwitterionic detergent and preferably is nonylphenoxypolyethyloxyethanol in a concentration in the range 0.1% to 10.0%, more preferably 0.5 to 5%, and still more preferably 0.6 to 1.8%. In a preferred embodiment, the surfactant is the anionic surfactant nonylphenoxypolyethyloxyethanol in a concentration of 1.6%. Other preferred anionic surfactants are anionic detergents including sodium lauryl sulfate, sodium dodecyl benzyne sulfate, potassium laurate, sodium dodecan sulfonate and members of the alkyl ether sulfate group (e.g., sodium lauryl ethoxysulfate). Other useful surfactants include a polyoxyethylene (POE) fatty acid ester such as nonionic surfactants prepared by esterification of fatty acids with ethylene oxide or polyethylene glycol. Commercially available surfactants that are polyoxyethylene esters of fatty acids include but are not limited to those sold under the following trademarks: EMULPHOR(copyright), ETHOFAT(copyright), LIPOPEG(copyright), NONISOL(copyright), PEGOSPERSE(copyright), STEROX CD(copyright) and VARONIC 400(copyright). Other useful nonionic surfactants are ethoxylates of fatty alcohols, such as Neodols, Tergitols, Genapols, Polytergents, Surfonics and Alfonics. Still other nonionic surfactants which are useful in the context of the present invention are the block polymers of ethylene oxide and propylene oxide, such as Pluronics and Tetronics. Additional available surfactants include but are not limited to mixtures of unesterified polyethylene glycols and mono- and distearate esters of polyethylene glycols (e.g., MAPEG 400 MS(copyright), EMEREST 2640(copyright)), and mixtures of mono- and distearate esters of polyoxyethylene and free POE (e.g., LIPAL 39S(copyright), MAPEG S 40(copyright), MYRJ 52S(copyright), PEGOSPERSE 1750-MS(copyright)). In addition to the foregoing, any of a variety of well known synthetic amphoteric, ampholytic, zwitterionic and cationic surfactants or mixtures of any of the types of surfactants well known in the art may be used.
Optionally, the treating solution can also include a chelating agent. The chelating agent allows the product to be used more easily in areas which have hard water, including most of the Western United States. Hard water promotes crystallization of the product in dispensing apparatuses such as xe2x80x9cHydroxe2x80x9d and xe2x80x9cDemaxe2x80x9d proportioners. These proportioners are well known in the art and work on the Venturi principle to allow varying the dilution of the product from 1:1 to 1:256 or more. A 1:256 dilution corresponds to one ounce of product per gallon of water. The chelating agent prevents crystallization by building the detergency of the solution.
In a preferred embodiment, the chelating agent has a neutral or near neutral pH (i.e., 6.5-7.5). Such chelating agents include, for example, sodium hexametaphosphate, tetrapotassium pyrophosphate, sodium tripolyphosphate and tetrasodium EDTA. We have achieved especially good results using sodium hexametaphosphate. The incorporation of acidic chelating agents into the floor cleaning solutions of the present invention is also contemplated. Such agents include, for example, sodium phosphonate, potassium phosphonate and organic phosphonates. The incorporation of other neutral, near neutral or acidic chelating agents into the instant floor cleaning solutions in also within the scope of the invention. In a preferred embodiment, the chelating agent is incorporated at a concentration from about 0.05% to about 2.0% in the full strength solution, but more preferably from about 0.1% to about 1.0%.
The pH of the solution used in the present invention should be adjusted carefully. The pH can be adjusted to an appropriate range using any of a variety of buffering agents well known in the art. Many of the treating agents are themselves buffers, such as ammonium bifluoride.
If the pH is too acidic, the solution is more hazardous and therefore not only can result in more injuries, but also requires additional precautions in transportation, storage and use. Further, too acidic a pH can lead to excessive etching, leading to high Rtm scores. Floors having excessively high Rtm scores have very deep xe2x80x9cvalleysxe2x80x9d between xe2x80x9cpeaks.xe2x80x9d These deep valleys form reservoirs for the accumulation of grease and other contaminants. Contaminants in these reservoirs can be extremely difficult to clean. Thus, high Rtm scores can, unexpectedly, actually result in lower COF""s. Therefore, the goal of restoration in the method of the present invention is to provide moderate Rtm scores which provide sufficient peaks and valleys to increase COF without creating deep reservoirs for accumulation of COF-lowering contaminants. Thus, we have unexpectedly discovered that moderate acidity results in the best performance.
In view of the foregoing, the method of the present invention makes use of treating solution having a pH in a range of between about 2.5 and 6.5, preferably between 3.0 and 6.0, more preferably between 4.0 and 5.5, and still more preferably about 4.5 to 5.0. In a particularly preferred embodiment using ammonium bifluoride at about 2.3-2.5%, the pH is about 4.85. Because the treating solution is not strongly acidic even when used full strength, it can be applied and mopped off the floor without first neutralizing or extensively rinsing to remove the solution.
The treating solution is preferably packed in 1 to 5 gallon containers which are preferably made of synthetic organic polymeric plastic material, such as polyvinyl chloride (PVC), polypropylene or polyethylene. If the treating solution contains a fluoride containing acid, care should be taken not to pack the solution in a glass container because the fluoride compounds can etch and weaken the glass. Treating solutions that do not contain fluoride compounds may be packed in glass, but for safety considerations, glass is less preferred because of the potential for cracking, breaking or shattering if dropped during use or transport of the solution in the container.
Because the treating solution is not highly acidic, transportation, storage and use will only require the ordinary level of care normally associated with potential exposure of skin to any agent which can act as a dermatological irritant. That is, when the treating solution is used at full strength or measured into a container for dilution for use in maintaining the floor, latex or similar impermeable gloves should preferably be worn to protect the hands and eyewear such as safety glasses or goggles should be worn to protect eyes from splashed liquid. Protective gloves and eyewear should preferably be worn during the entire cleaning process.
The general principles of the present invention may be more fully appreciated by reference to the following non-limiting examples.